how to know if a program is older than another one

I created a program that people use. I want to let them know if I updated my program. How can I check if the program they run is older than the original file? (they make a copy of the original)

I created a program that people use. I want to let them know if I updated my program. How can I check if the program they run is older than the original file? (they make a copy of the original)
You could create a server that stores the current version of your program (this could be a web page or whatever), then write your program to ocassionally check that version against the version that they are running. If the indicated current version is newer than the version they are running, popup a message to let your user know that there is a newer version available.